(a) Technical Field
The present invention relates to a technique for compensating for an abnormal output of a resolver for an environmentally friendly vehicle. More particularly, it relates to a method for compensating for an abnormal output of a resolver for an environmentally friendly vehicle, which prevents the occurrence of errors in the rotor position angle and speed estimation of a motor due to an abnormal AD conversion error in a resolver-to-digital converter (RDC).
(b) Background Art
Typically, a drive motor for converting electrical energy into mechanical energy and an inverter for controlling the operation of the drive motor are mounted in environmentally friendly vehicles such as hybrid vehicles, electric vehicles, hydrogen fuel cell vehicles, etc.
As shown in FIG. 3, the inverter 100 includes: a power module 101 (e.g., an insulated gate bipolar transistor, IGBT) which transmits electrical energy between a battery 110 and an interior permanent magnet synchronous motor (IPMSM) 120. A direct current (DC) link capacitor 102 absorbs the ripple component of DC voltage caused by the operation of the inverter 100 to prevent the ripple component from being transmitted to the battery 110. A DC link voltage sensor 103 measures the DC voltage of the inverter 100, i.e., the voltage at both ends of the DC link capacitor 102 to be used to control the inverter 100. A DC link voltage sensing circuit 104 processes the output of the DC link voltage sensor 103 to have a magnitude capable of being input to an analog/digital (AD) converter and, at the same time, prevents the occurrence of a voltage measurement error due to noise, etc.
A current sensor 105 measures the alternating current of the inverter 100 to be used to control the inverter 100 and a current sensing circuit 106 processes the output of a current sensor in a current sensor module to have a magnitude capable of being input to the AD converter and, at the same time, prevents the occurrence of a current measurement error due to noise, etc. A central processing unit (CPU) 107 is equipped with a software program stored on a computer readable medium that is executed by a processor to control the inverter 100 and the overall operation of the inverter 100 by using measured physical parameters received from the sensors 103 and 105. A control/gate board 108 is equipped with the above-described circuits and components used to control the inverter 100.
More specifically, however, a resolver 122 in automotive applications detects the speed of the motor and the angle of a rotor that is used in the synchronous motor 120. Thus, the sensing and failure detection of the resolver 122 is one of the most important factors in controlling the motor effectively.
At present, as shown in FIG. 4, the occurrence of a failure in the resolver 122 is conventionally detected as follows. In the event of a failure in input signals (i.e., excitation signals, EXT+, EXT−) or output signals (i.e., basic signals for measuring the speed, S1-S3, S2-S4) of the resolver 122, a FAULT signal is generated by a resolver-to-digital converter (RDC) 124, and the digital FAULT signal transmitted to the CPU 107 is input to a CPU, e.g., a motor controller, thereby detecting the occurrence of a failure in the resolver 122.
However, when the voltage margin is reduced by the maximum torque operation of the motor at high temperature and at low speed and during overmodulation, the occurrence of an abnormal AD conversion error in the RDC causes errors in the rotor position angle and speed estimation of the motor, which are used to control the motor. Therefore, due to the absence of resolver position information, the temperature of the motor is increased, the controllability of the motor current is reduced, and an overcurrent occurs in the motor. As a result, the hybrid function of a hybrid vehicle may be disabled. Even worse, in some instances the operation of the electric vehicle and the hybrid vehicle may be disabled completely unnecessarily.
The above information disclosed in this Background section is only for enhancement of understanding of the background of the invention and therefore it may contain information that does not form the prior art that is already known in this country to a person of ordinary skill in the art.